Transparent failover is a known example of technology for enhancing the availability of a distributed database management system. In the transparent failover, even when an abnormality occurs in a distributed server or in a connection path to a distributed server in the course of processing of a request from an application, the connection destination of the application is automatically switched to another distributed server.
A method of implementing failover is different depending on a data model of a distributed database to be operated or operation contents. For example, in a distributed key-value store involving no transaction control, failover can be implemented by repeatedly issuing a registration request until a normal response is obtained from an appropriately selected distributed server. For a distributed database involving transaction control, transparent failover based on a distributed protocol, such as the three-phase commit protocol, is known.